The present invention is directed to a method and apparatus for controlling blood volume and hydration, and for indicating resuscitation status of a patient using peripheral venous pressure as a hemodynamic parameter.
Patients undergoing major surgery are at risk for significant blood loss and hemodynamic changes while under anesthesia. A portion of that risk is associated with the surgery itself, and the remainder is attributable of the effects of anesthetics, mechanical ventilation, positional changes on cardiac function, relative blood volume, and vascular tone. Oxygen carrying capacity as well as the body""s efficiency in removing carbon dioxide and metabolic wastes are a function of blood volume.
For patients having procedures with a likelihood of significant blood loss, or for patients in whom hemodynamic changes are especially threatening because of coincident cardiovascular disease, central venous pressure (xe2x80x9cCVPxe2x80x9d) monitoring has been widely used. CVP is a direct measure of blood pressure, not blood volume. In a normal range of hemodynamic values, CVP appears to have more utility as a trend monitor than for titration to an absolute end point.
The measurement of CVP requires the insertion and maintenance of a catheter in the thorax. Typically, the catheter is positioned in the superior vena cava from an insertion site in an external or internal jugular vein, subclavian vein, or, less often, from a femoral or antecubital vein. CVP placement adds time and monetary costs to surgery. Also, CVP measurements typically include respiratory variations and cardiac excursions that must be considered during monitoring.
The need to control blood volume and hydration and assess resuscitation status are particularly important in neurosurgical patients undergoing either craniotomy or complex spine surgery. It is also important to control hydration in hospitalized patients as well as nursing home patients.
In accordance with the present invention, control of blood volume and hydration, and indicating resuscitation status of a patient is achieved using peripheral venous pressure as a hemodynamic parameter. The present invention is useful for patients undergoing surgery or trauma patients as well as hospitalized patients and nursing home patients.
In accordance with one aspect of the present invention, an apparatus for measuring peripheral venous pressure in a patient comprises a fluid source and a fluid conduit for carrying fluid from the fluid source to the patient. A pump pumps fluid from the fluid source to the patient through the fluid conduit. The apparatus further includes means for measuring fluid pressure in the fluid conduit indicative of the peripheral venous pressure of the patient.
In accordance with another aspect of the present invention, an apparatus comprises a fluid source, a pump for pumping fluid from the fluid source to a patient, means for measuring a value functionally related to mean systemic pressure of the patient, and means for controlling the pump in response to the measured value functionally related to the mean systemic pressure of the patient.
In accordance with another aspect of the present invention, an apparatus comprises a fluid source, a pump for pumping fluid from the fluid source to a patient, means for measuring peripheral venous pressure of the patient, and means for controlling the pump in response to the measured peripheral venous pressure of the patient.
In accordance with still another aspect of the present invention, an apparatus for controlling fluid volume in a patient comprises a fluid source and a fluid conduit for carrying fluid from the fluid source to the patient. A controllable infusion pump pumps fluid from the fluid source to a peripheral vein of the patient through the fluid conduit. An occluder blocks fluid communication through the fluid conduit between the fluid source and the patient. A fluid pressure sensor senses fluid pressure in the fluid conduit. The apparatus further includes a controller for determining a peripheral venous pressure value from the sensed fluid pressure in the fluid conduit after the infusion pump is stopped and the occluder blocks the fluid communication through the fluid conduit between the fluid source and the patient. The peripheral venous pressure is indicative of fluid volume of the patient.
In accordance with still another aspect of the present invention, an apparatus for controlling fluid volume in a patient comprises a fluid source and a controllable infusion pump connected to the fluid source through a fluid inlet line. The apparatus includes a catheter inserted in a peripheral vein of a patient and connected from an outlet of the infusion pump through a fluid outlet line so as to provide a fluid communication path between the peripheral vein of the patient and the pump. Activation of the pump results in fluid being delivered to the patient from the fluid source through the catheter. An in-line pressure sensor is positioned substantially at a heart level of the patient for sensing pressure in the fluid communication path and providing a pressure measurement signal indicative thereof. The apparatus further includes an actuatable in-line occluder for isolating the fluid source from the patient when the occluder is actuated and control means for periodically stopping the infusion pump, actuating the occluder, monitoring the pressure measurement signal, and determining a peripheral venous pressure value of the patient in response thereto. Means are provided for adjusting operation of the infusion pump in response to the determined peripheral venous pressure value.
In accordance with another aspect of the present invention, a method for measuring peripheral venous pressure in a patient comprises the steps of connecting a fluid source to the patient through a fluid conduit, pumping fluid from the fluid source to the patient through the fluid conduit, and measuring fluid pressure in the fluid conduit indicative of the peripheral venous pressure of the patient.
In accordance with another aspect of the present invention a method comprises the steps of pumping fluid from a fluid source to a patient, measuring a value functionally related to mean systemic pressure of the patient, and controlling the pumping in response to the measured value functionally related to mean systemic pressure of the patient.
In accordance with another aspect of the present invention, a method comprises the steps of pumping fluid from a fluid source to a patient, measuring peripheral venous pressure of the patient, and controlling the pumping in response to the measured peripheral venous pressure of the patient.
In accordance with yet another aspect of the present invention, a method for controlling fluid volume in a patient comprises the steps of connecting a fluid source to the patient through a fluid conduit, periodically pumping fluid with an infusion pump from the fluid source to a vein of the patient through the fluid conduit, periodically occluding fluid communication through the fluid conduit between the fluid source and the patient, periodically sensing fluid pressure in the fluid conduit, monitoring the sensed fluid pressure in the fluid conduit after (i) pumping stops, and (ii) occluding blocks the fluid communication through the fluid conduit between the fluid source and the patient, and providing an indication of the monitored fluid pressure, the monitored fluid pressure being indicative of fluid volume of the patient.